The present invention relates to washing machines and more particularly to moving clothes within the wash chamber of an automatic washer.
Known washing machines include vertical axis washers that use an agitator, impeller or some other type of rotor that rotates or oscillates about a vertical axis, such as shown in U.S. Pat. Nos. 5,031,427 and 5,460,018 or horizontal axis machines that input mechanical energy to the clothes load by rotating the wash chamber at a speed less than that which could cause the clothes to be held against the wall of the wash chamber by centrifugal force. Such horizontal axis machines are disclosed in U.S. Pat. Nos. 5,219,370 and 5,974,610.
In such typical horizontal or tilted axis washing machines, the wash chamber rotations or oscillations are symmetric and constant during the majority of a wash cycle. That is, they use a set, non-changing clockwise and counter clockwise wash chamber oscillation. In a vertical axis machine, typically there is a center rotor in the form of an agitator or impeller that rotates to impart mechanical energy to the wash load, and typically those rotations are symmetric and constant during the majority of the wash cycle. The wash chamber may be rotatable, but typically the wash chamber is rotated only during an extraction mode when it is desired to remove water or wash liquid from the clothes load, and then the wash chamber is spun in one direction only.
FIG. 1 depicts a typical symmetrical wash chamber oscillation period during a typical wash cycle in a horizontal or tilted axis washer. In FIG. 1, signals above the horizontal time axis indicate a clockwise rotation signal, signals along the time axis indicate no rotation signal (motor off) or a pause, and signals below the time axis indicate a counter-clockwise rotation signal. The illustrated oscillation period includes a 0.5 second clockwise (motor on) time, followed by a 0.5 second pause (motor off), followed by a reversing 0.5 second counter-clockwise (motor on) time, followed by a 0.5 second pause (motor off). The oscillations are constant, in that the period is then repeated. In some horizontal axis machines, the oscillation cycles may be longer or shorter, such as an 8 second clockwise rotation, 8 second pause, 8 second counter clockwise rotation and 8 second pause. A more complex pattern may also be provided, such as an 8 second clockwise rotation, 2 second pause, 8 second counter clockwise rotation and 2 second pause. However, whatever the individual pattern is for a given period, it is this same pattern that is repeated for all periods.
In U.S. Ser. No. 10/142,345, assigned to Whirlpool Corporation, assignee of the present application, the washer oscillates the clothes load for a plurality of periods of clockwise and counter-clockwise oscillations, wherein the time duration of the oscillations are selected for each period. The oscillations can be symmetrical or asymmetrical, and can have a time duration that is variable. Further, in another embodiment, the time duration of the oscillations varies for consecutive periods.
The tumbling action of the clothes load in a washer results in a flexing of the fabric to loosen and remove dirt and other foreign materials from the fabric load, but it also causes mechanical damage to the fabric in the form of broken threads. A reduction in such damage would be desirable, particularly if the level of dirt and foreign material removal can be maintained or enhanced.